Chapter 15. Weakly Typed Object SQL
Weakly typed
object SQL refers to the use of
structures, arrays, and references to insert, update, delete, and
select SQL objects. A
structure refers to
a structured SQL data type, which is a user-defined SQL
data type synonymous with a Java
class. An array refers to a SQL ARRAY, and a reference refers to a
SQL REF. These SQL data types are represented in JDBC by the
java.sql.Struct,
java.sql.Array, and
java.sql.Ref interfaces. A
Struct is a JDBC object that retrieves a database
object. It represents the locator for a structured SQL data type, or
database object, in your Java program. After retrieving a database
object with a Struct, you retrieve the
object’s attributes by calling its getAttributes( ) method, which returns a Java Object
array. Since the attributes are returned as an
Object array, it’s up to you, the
programmer, to properly cast each object value as it is used. Hence,
a Struct is weakly typed. If, in turn, an
attribute of the Struct represents another
structured SQL data type, or database object, then that attribute
must itself be cast to the Struct. Likewise, if
the attribute of a Struct is an array of values,
such as an Oracle varying array or nested table, then you must cast
that attribute to another JDBC object type, an
Array.
Similar to a Struct, an Array
represents the locator for a SQL ARRAY. It has a method,
getArray( ), which returns the database array
values as a Java Object array. If an element of
the returned Object ...
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